Japan’s Financial Services Agency (FSA) is planning to implement new rules to enhance the security of cold wallets that are used to store cryptocurrencies at crypto exchanges, Reuters reported.

An anonymous source familiar with the matter told the media giant that the FSA will require crypto exchanges to strengthen the measures to supervise cold wallets.

The regulator has already restricted the use of “hot wallets” which are “online wallets” and more prone to attacks. This led crypto exchanges to switch to cold storage, which is not connected to the internet and therefore less vulnerable to hacks.

However, the FSA has now turned its focus on cold wallets, after it determined that there are risks of internal thefts, the source added. Some exchanges have reportedly failed to introduce rules to regularly rotate out the person in charge of the storage, the source said.

In April 2017, Japan revised its Payment Services Act which requires all cryptocurrency exchange operators to register with FSA. Importantly, it recognized bitcoin as a means of payment in the country.

A total of 19 crypto exchanges have been officially registered in the country to date, including Rakuten Wallet.

Last month, the Cabinet of Japan approved draft amendments to the country’s financial instruments and payment services laws, which will introduce new regulations for crypto margin trading, Nikkei reported.